Mauricio Pochettino apologised to fans for what he described as his worst result as a manager after Tottenham's 5-1 defeat by Newcastle.
Spurs ended the season in third place, behind rivals Arsenal for the 21st consecutive season, drawing two and losing two of their final four games of the season.
Pochettino, who signed a new five-year deal with Spurs in midweek, could not hide his disappointment at the performance, and insists his players' mentality was to blame.
He told Sky Sports: "I'm very disappointed; it was my worse game as a manager. We spoke weeks before about never giving up, we need to learn and improve our mentality.
"Firstly I want to apologise to our fans, our supporters, it was a shame what happened on the pitch.
"I apologise to our families, the families who have suffered behind us, it is difficult now to arrive home and explain what has happened here.
"When you watch the game it wasn't a tactical problem, a skill or technical problem, it was a mental problem. When you go on the pitch you need to give 100 per cent. We need to show more character."
Tottenham were Leicester's nearest challengers for the title for the majority of the season, but after their 2-2 draw with Chelsea at the beginning of the month, Pochettino's side have faltered.
The Argentine says he challenged his players to keep their mental edge after that disappointing result, and added that these types of performances cannot be repeated.
"Yes [the Chelsea result was difficult to take], this was our challenge, to keep the mentality. After Chelsea we showed a lot of weakness, against Southampton and today. This cannot repeat again.
"First of all, it is my responsibility, but I am disappointed. I think we need to analyse now, we are third in the table.
"But it's not about the result, today the first 45 minutes was bad, and in the second we conceded three goals against 10 players."